1. Field of the Invention
The present invention relates to an optical entire-circumference encoder and a motor system.
2. Discussion of the Background
Optical encoders are used to measure physical quantities, such as position and speed, of moving objects. Some optical encoders use fixed slits corresponding to rotating slits formed on a disc so as to cause reflected light or transmitted light to occur corresponding to rotation of the disc. For highly accurate position detection, such optical encoders require highly accurate adjustment of the position relationship between the rotating slits and the fixed slits. This is because if an error exists in the position relationship between the fixed slits and the rotating slits, the error causes reflected light and transmitted light unnecessary in design viewpoints to be received by the photodetector, resulting in increased noise. To reduce such noise, rotary encoders of optical entire-circumference correction type (hereinafter also referred to as “optical entire-circumference encoders”) are under development (see, for example, Japanese Translation of PCT International Application Publication No. 2006-515426).